cnn's susan candiotti is also here in newtown. and she has been tracking the investigation both at the school and at the suspected killer's home. >> reporter: investigators are learning more each day that may explain what led 20-year-old adam lanza to launch a vicious attack on young children and adults at an elementary school. >> our investigators at the crime scene, the school and secondarily at the secondary crime scene that we discussed where the female was located deceased, did produce some very good evidence in this investigation that our investigators will be able to use in hopefully painting the complete picture as to how and more importantly why this occurred. >> reporter: police won't say that what evidence is. however, investigators have been checking out gun ranges and sporting goods stores. they followed a lead the shooter tried to buy a gun tuesday at this location. after searching store surveillance videos, the tip didn't pan out. >> to date, atf has not uncovered any information that would substantiate the fact tha